MongoDB Java使用指南

MongoDB是当今非常流行的一款NoSQL数据库，本文介绍如何使用MongoDB的Java驱动来操作MongoDB。 

一、引入MongoDB Java Driver包

如果需要操作MongoDB的Java项目是一个Maven项目，可以在依赖中加上以下的配置。

<code class="language-xml hljs  has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">dependencies</span>></span>    <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">dependency</span>></span>        <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">groupId</span>></span>org.mongodb<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">groupId</span>></span>        <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">artifactId</span>></span>mongo-java-driver<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">artifactId</span>></span>        <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"><<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">version</span>></span>2.13.2<span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">version</span>></span>    <span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">dependency</span>></span><span class="hljs-tag" style="color: rgb(0, 102, 102); box-sizing: border-box;"></<span class="hljs-title" style="box-sizing: border-box; color: rgb(0, 0, 136);">dependencies</span>></span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li></ul>

或者通过直接下载jar包的方式使用，下载地址：mongo-java-driver-2.13.2.jar。 
详细的如何引入MongoDB jar包的方法可以参考官方文档。

二、连接MongoDB

可以使用MongoClient来连接MongoDB，MongoClient的使用方式如下：

<code class="language-Java hljs cs has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">MongoClient mongoClient = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> MongoClient(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"localhost"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">27017</span>);DB db = mongoClient.getDB(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mydb"</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

上面的代码连接了localhost:27017上MongoDB服务，并指定使用mydb数据库。连接后便可以对这个数据库作进一步的操作。 
需要指出的是，MongoClient是线程安全的，可以在多程程环境中共享同一个MongoClient。通常来说，一个应用程序中，只需要生成一个全局的MongoClient实例，然后在程序的其他地方使用这个实例即可。

三、认证

可以使用多种方式对连接进行认证，下面介绍两种方式。

1. 方式一：MongoCredential

MongoCredential类的createCredential方法可以指定认证的用户名，密码，以及使用的数据库，并返回一个MongoCredential对象。其方法的声明如下：

<code class="hljs vbnet has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">static</span> MongoCredential createCredential(<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">String</span> userName, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">String</span> database, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">char</span>[] password)</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

例如，

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">MongoCredential credential = MongoCredential<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.createCredential</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"user"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mydb"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"password"</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.toCharArray</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

上面创建了一个用户名为user，密码为password，数据库为mydb的MongoCredential对象。 
将生成MongoCredential的对象作为MongoClient构造函数的参数。由于MongoClient构造函数的为List<MongoCredential>类型，所以需要先构造成一个List再传递。完整的认证的例子如下：

<code class="language-Java hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">MongoCredential credential = MongoCredential<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.createCredential</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"user"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mydb"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"password"</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.toCharArray</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; </span>ServerAddress serverAddress = new ServerAddress(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"localhost"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">27017</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; </span>MongoClient mongoClient = new MongoClient(serverAddress, Arrays<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.asList</span>(credential))<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">; </span>DB db = mongoClient<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getDB</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mydb"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

2. 方式二：MongoClientURI

亦可以使用MongoClientURI完成MongoDB的认证，它代表了一个URI对象。MongoClientURI的构造函数接受一个String类型的字符串，这个字符串的格式如下：

mongodb://[username:password@]host1[:port1][,host2[:port2],…[,hostN[:portN]]][/[database][?options]]

生成的MongoClientURI对象作为MongoClient构造函数的参数，完整的认证例子如下：

<code class="language-Java hljs perl has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">String sURI = String.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">format</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mongodb://<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">%s</span>:<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">%s</span><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">@%</span>s:<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">%d</span>/<span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">%s</span>"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"user"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"password"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"localhost"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">27017</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mydb"</span>); MongoClientURI uri = new MongoClientURI(sURI); MongoClient mongoClient = new MongoClient(uri); DB db = mongoClient.getDB(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mydb"</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li></ul>

四、获取一个集合

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">DBCollection coll = db<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.getCollection</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mycol"</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li></ul>

然后可以对指定的集合进行操作，例如，插入，删除，查找，更新文档等。

五、插入文档

例如，一个文档以Json来表示如下，

{ “name”: “mongo”, “info”: { “ver”: “3.0” } }

现在需要插入到集合mycol中。为了插入到集合中，可以使用BasicDBObject构造一个文档。

<code class="hljs go has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">BasicDBObject doc = <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">new</span> BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"name"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"mongo"</span>).<span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">append</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"info"</span>, <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">new</span> BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"ver"</span>, <span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"3.0"</span>));coll.insert(doc);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

六、查找文档

1. 通过findOne查找一个符合条件文档

通过findOne可以查找一个符合条件的文档。例如，对于上面的mycol集合，执行以下命令：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">DBObject myDoc = coll<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.findOne</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(myDoc)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

将输出mycol集合中的第一个文档。也可以通过指定findOne的查找参数，来查找符合查找条件的一个文档。

2. 通过find查找所有符合条件的文档

find用来查找符合条件的文档，它返回一个DBCursor对象，通过遍历DBCursor对象，可以获得所有符合查找条件的文档。 
为了说明和测试，我们先插入一批以下格式的文档

{ “i”: value }

<code class="hljs matlab has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">for</span> (int <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">i</span>=<span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">0</span>; <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">i</span> < <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>; <span class="hljs-built_in" style="color: rgb(102, 0, 102); box-sizing: border-box;">i</span>++) <span class="hljs-cell" style="box-sizing: border-box;">{    coll.insert(new BasicDBObject("i", i));}</span></code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

find的使用示例如下：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">DBCursor cursor = coll<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.find</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>try {   while(cursor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.hasNext</span>()) {       System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(cursor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.next</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>   }} finally {   cursor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.close</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li></ul>

会输出mycol集合中所有的文档。 
也可以指定查找的条件，例如：

<code class="hljs avrasm has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">BasicDBObject query = new BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">71</span>)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>DBCursor cursor = coll<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.find</span>(query)<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>try {   while(cursor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.hasNext</span>()) {       System<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.out</span><span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.println</span>(cursor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.next</span>())<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>   }} finally {   cursor<span class="hljs-preprocessor" style="color: rgb(68, 68, 68); box-sizing: border-box;">.close</span>()<span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">;</span>}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

对于查找条件中包括$操作符的情形，例如以下一条mongo shell命令：

db.coll.find({i: {$gte: 50}});

可以使用DBObject生成查找条件，

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-comment" style="color: rgb(136, 0, 0); box-sizing: border-box;">// find all where i >= 50</span>BasicDBObject query = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i"</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"$gte"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">50</span>));DBCursor cursor = coll.find(query);<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">try</span> {    <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">while</span> (cursor.hasNext()) {        System.<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">out</span>.println(cursor.next());    }} <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">finally</span> {    cursor.close();}</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li><li style="box-sizing: border-box; padding: 0px 5px;">4</li><li style="box-sizing: border-box; padding: 0px 5px;">5</li><li style="box-sizing: border-box; padding: 0px 5px;">6</li><li style="box-sizing: border-box; padding: 0px 5px;">7</li><li style="box-sizing: border-box; padding: 0px 5px;">8</li><li style="box-sizing: border-box; padding: 0px 5px;">9</li><li style="box-sizing: border-box; padding: 0px 5px;">10</li><li style="box-sizing: border-box; padding: 0px 5px;">11</li></ul>

七、更新文档

<code class="hljs cs has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;">BasicDBObject query = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">70</span>);BasicDBObject up = <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"$set"</span>, <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">new</span> BasicDBObject(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">100</span>));coll.update(query, up);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li><li style="box-sizing: border-box; padding: 0px 5px;">3</li></ul>

上面的语句将i为70的文档更新i的值等于100。 
与我们常用的更新文档的mongo语句一样，DBCollection还包含了save，findAndModify等更新文档的方法，其使用方法在此不再赘述，可以参考API说明文档即可。

八、删除文档

可以通过生成一个DBObject对象来删除指定的文档，例如：

<code class="hljs erlang has-numbering" style="display: block; padding: 0px; background-color: transparent; color: inherit; box-sizing: border-box; font-family: 'Source Code Pro', monospace;font-size:undefined; white-space: pre; border-top-left-radius: 0px; border-top-right-radius: 0px; border-bottom-right-radius: 0px; border-bottom-left-radius: 0px; word-wrap: normal; background-position: initial initial; background-repeat: initial initial;"><span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">BasicDBObject</span> <span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">query</span> = new <span class="hljs-variable" style="color: rgb(102, 0, 102); box-sizing: border-box;">BasicDBObject</span>(<span class="hljs-string" style="color: rgb(0, 136, 0); box-sizing: border-box;">"i"</span>, <span class="hljs-number" style="color: rgb(0, 102, 102); box-sizing: border-box;">71</span>);coll.remove(<span class="hljs-keyword" style="color: rgb(0, 0, 136); box-sizing: border-box;">query</span>);</code><ul class="pre-numbering" style="box-sizing: border-box; position: absolute; width: 50px; background-color: rgb(238, 238, 238); top: 0px; left: 0px; margin: 0px; padding: 6px 0px 40px; border-right-width: 1px; border-right-style: solid; border-right-color: rgb(221, 221, 221); list-style: none; text-align: right;"><li style="box-sizing: border-box; padding: 0px 5px;">1</li><li style="box-sizing: border-box; padding: 0px 5px;">2</li></ul>

上面的语句删除i为71的文档。

九、参考资料

• http://mongodb.github.io/mongo-java-driver/2.13/getting-started/installation-guide/
• http://mongodb.github.io/mongo-java-driver/2.13/getting-started/quick-tour/
• https://github.com/mongodb/mongo-java-driver/blob/2.13.x/src/examples/example/QuickTour.java
• http://mongodb.github.io/mongo-java-driver/3.0/driver/reference/connecting/authenticating/
• http://api.mongodb.org/java/3.0/?com/mongodb/MongoClientURI.html
• http://api.mongodb.org/java/2.13/

转载于：http://blog.csdn.net/lihao21/article/details/46939269